JP3423644B2 - Projection optical system and projection exposure apparatus using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical system and a projection exposure apparatus using the projection optical system, for example IC, LSI, C.
In a step-and-repeat type or step-and-scan type projection exposure apparatus, which is a manufacturing apparatus for various devices such as a CD, a liquid crystal panel, and a magnetic head, an original plate such as a photomask or a reticle (hereinafter referred to as a "reticle").
It is suitable for manufacturing a device by projecting and transferring the above circuit pattern onto a wafer surface (photosensitive substrate) coated with a photosensitive agent.

[0002]

2. Description of the Related Art The recent progress in manufacturing technology of devices such as semiconductor elements is remarkable, and accompanying it, the progress of fine processing technology is remarkable. In particular, the optical processing technology is mainly a reduction projection exposure device with a submicron resolution, commonly known as a stepper. To further improve the resolution, it is possible to increase the numerical aperture (NA) of the projection optical system and shorten the exposure wavelength. Has been.

Conventionally, a projection exposure apparatus has been used for IC, LS
A projection optical system for printing a semiconductor element pattern such as I on a wafer such as silicon requires very high resolution.

Generally, the resolution of a projected image by a projection optical system is improved as the wavelength used is shortened. Therefore, a light source which emits light having a wavelength as short as possible is used. For example, as a light source that emits light of a short wavelength, an excimer laser has received attention. This excimer laser uses ArF, KrF or the like as a laser medium.

By the way, in the wavelength range of this light source, the glass materials usable as lens materials are limited to quartz and fluorite. This is mainly due to the decrease in transmittance,
Even in the case of quartz or fluorite, an optical system having a large number of lenses and a large total thickness of glass material as in the prior art causes a problem such as a change in focal position due to heat absorption of the lens.

Conventionally, a projection optical system in which all lenses are spherical surfaces is disclosed in, for example, Japanese Patent Laid-Open No. 9-105861.
JP-A-10-48517 and JP-A-10-7934.
No. 5, etc. are proposed. Further, in order to reduce the maximum effective diameter, a projection lens composed of seven lens groups having positive, negative, positive, negative, positive, negative and positive refractive powers in order from the object side is disclosed in Japanese Patent Laid-Open No. -48517.

A projection optical system that corrects aberrations by using an aspherical surface is disclosed, for example, in Japanese Patent Publication No. 7-048089.
JP-A-7-128592 and JP-A-5-03459.
No. 3, JP-A-10-197791, JP-A No. 1-197791
No. 0-154657 and Japanese Patent Laid-Open No. 10-325922 are proposed.

[0008]

Generally, in order to obtain high imaging performance (optical performance), for example, the refractive power of each lens group is reduced to reduce the amount of aberration generated, or the lens of each lens group is reduced. It is necessary to increase the degree of freedom in aberration correction by increasing the number of sheets.

Taking the projection exposure apparatus as an example, the "imaging performance" refers to the best image plane based on the line width (pattern line width) in addition to the correction status of various aberrations such as spherical aberration and coma. It refers to various performances such as a change in position, a change in image point position due to each image height, a change in contrast, a change in distortion between different illumination conditions, and a change in image plane flatness.

The change in the best image plane position due to the line width is caused by the uncorrected residual spherical aberration. The change of the image point position and the change of the contrast with each image height are caused by the change of the sagittal, meridional image plane, the astigmatism, and the coma at each image height.

The change in distortion and the change in image plane flatness between the illumination conditions are caused by the residual amount of distortion and the aberration amount in the light beam passing region on the pupil under each illumination condition. These aberration changes become more remarkable as the pursuit of shorter wavelength, higher NA, securing a wider exposure area, and the like.

For this reason, when an attempt is made to achieve a projection optical system having a high numerical aperture and a wide exposure area, the distance between the lens object images becomes large, the lens diameter and the number of lenses increase, and the like. The problem arises that the entire system becomes thicker and larger.

Further, if an attempt is made to achieve a projection optical system having a high numerical aperture and a wide exposure area within a limited distance between lens object images, the number of lenses also increases, so that the lens thickness is thin. It increases self-weight deformation. If the self-weight deformation becomes large, the radii of curvature of both surfaces of the lens will deviate from the designed values, and the imaging performance will deteriorate.

In recent years, due to the industrial trend of high integration, there is a demand for further shortening of the wavelength of the exposure light source and further higher NA of the projection optical system. However, achieving the target optical performance has become extremely difficult. Particularly, in the conventional example, the aberration correction is not sufficient, and further improvement of the imaging performance is desired.

JP-A-9-105861 and JP-A-1
In the projection optical system proposed in Japanese Unexamined Patent Publication No. 0-48517 and Japanese Unexamined Patent Publication No. 10-79345, all the lenses are spherical, and the number of lenses is 27 to 30.
NA is about 0.5 to 0.6.

Attempting to achieve a high NA in this state makes it very difficult to correct aberrations if the number of lenses is maintained as it is. Otherwise, the total lens length must be increased and the lens diameter also increased. I will end up. Even if an attempt is made to correct aberrations by further increasing the number of lenses, there is almost no space for adding lenses, so it is necessary to reduce the thickness of each lens or otherwise increase the total lens length.

In any case, the above-mentioned self-weight deformation increases, and the entire lens system also increases in size. In addition, as described above, in the short wavelength region of the light source, the absorption decreases due to the large absorption by the lens material, but in an optical system with a large number of lens constituents such as this conventional example, on the wafer Since the light exposure amount of 1 is further reduced, the throughput is also reduced, and the fluctuation of the focal position due to the heat absorption of the lens, the fluctuation of the aberration, etc. are also increased.

Particularly, Japanese Patent Laid-Open No. 10-48517 discloses that
This is a projection lens aiming to reduce the maximum effective diameter by composing seven lens groups of positive, negative, positive, negative, positive, negative, and positive refractive power from the object side.

According to the description in the text, this projection lens arranges the groups having positive refracting power and the groups having negative refracting power alternately so that the luminous flux diverged by the group having negative refracting power is changed. It converges in a group having a positive refracting power before it spreads so much, and by repeating this, the negative refracting power is dispersed and the Petzval sum is improved.

However, the number of constituents is very large, about 30, the NA is small, about 0.6, and the object-image distance is large, about 1140 to 1200 mm. It is very difficult to achieve NA and high performance.

Further, Japanese Patent Publication No. 7-4808 using an aspherical surface.
The projection optical system disclosed in Japanese Patent Laid-Open No. 9-128592 and Japanese Patent Laid-Open No. 7-128592 is not a telecentric optical system on the object side, and there is a concern that the warp of the object surface (reticle surface) may affect image distortion.

Further, the projection optical system proposed in JP-A-5-34593, JP-A-10-197791 and the like is composed of a both-side telecentric system, and the refracting powers of the lens units are arranged in order from the object side. Is composed of four groups of positive, negative, positive, and positive. However, a lens system with a high numerical aperture has not been achieved, and there is a risk that the effective diameter will become too large when attempting to achieve a higher NA.
Further, if an attempt is made to reduce the effective diameter, the refractive power of each group becomes too strong, which makes it difficult to correct aberrations satisfactorily.

In Japanese Patent Laid-Open No. 10-154657, an aspherical lens is used in the lens system. This aspherical surface is used to realize a projection optical system having a desired specification as described. , Unlike the aspherical surface introduced to positively correct the aberration at the time of design, the projection optical system is assembled and manufactured using a plurality of optical members, for example, the manufacturing error of the optical component itself when assembled and adjusted. In addition, residual high-order aberrations that are difficult to remove due to adjustment errors of the projection optical system are corrected.

That is, since all optical design is performed by the spherical system, even if the manufacturing error is corrected by the aspherical surface, the product cannot achieve the performance exceeding the design value of the spherical system. Therefore, the amount of aspherical surface is very small. Therefore, it is very difficult to solve the above-mentioned problems even if it is attempted to cope with the high NA as it is.

According to Japanese Patent Laid-Open No. 10-325922, the projection optical system is composed of five lens groups, and one of the first lens group and the second lens group does not have one surface. By using a spherical surface and an aspherical surface on one surface of either the fourth lens group or the fifth lens group, distortion and spherical aberration are mainly corrected with a small number of constituent elements. The example has an NA of 0.6.

Moreover, there is no embodiment using an aspherical surface in the fourth lens group, and although field curvature and astigmatism are relatively well corrected in terms of aberration, the high-order component of spherical aberration is largely under. Has occurred, and distortion is 30n at the maximum image height.
It is about m.

There is a large gap between the purpose of using the proposed aspherical surface and the embodiment, and it cannot be said that the aspherical surface is effectively used. In the text, an aspherical surface is used as a surface having a large correction effect, but there is no further detailed description.

Therefore, even if an attempt is made to further increase the NA, deterioration of the aberration is inevitable. Further, when trying to deal with this by increasing the degree of freedom in correction by increasing the number of lenses, a relatively large space remains on the image plane side, so even if spherical aberration can be corrected, the third group from the first group on the object side to the third group can be corrected.
Since the lenses are densely continuous in the group and there is no space to add a new lens, field curvature, astigmatism,
It becomes difficult to correct distortion and the like. If the center thickness of the lens is reduced and added, the problem of self-weight deformation described above will occur.

According to the present invention, by effectively using the aspherical surface,
An object of the present invention is to achieve a projection optical system which has a small number of constituent lenses and can secure a high resolution and a wide exposure area, and a projection exposure apparatus using the projection optical system.

[0030]

A projection optical system according to a first aspect of the present invention is a projection optical system for projecting an image of an object onto an image plane, wherein the projection optical system has a positive refractive power in order from the object side. The first lens group L1 has, the second lens group L2 having negative refractive power, and the third lens group L3 having positive refractive power.
A fourth lens group L4 having a negative refractive power, a fifth lens group L5 having a positive refractive power, a sixth lens group L6 having a negative refractive power, and a lens group L7 having a positive refractive power. Where L is the conjugate length of the projection optical system and φo is the total power of the negative lens groups, 70> | L × φo |> 17 (φo = Σφoi; φoi is the i-th negative group) Power) (1), where h is the height of the axial marginal ray and hb is the height of the most off-axis chief ray, 15> | hb / h |> 0.35 At least two of the surfaces satisfying 2) are aspherical surfaces,
For at least two aspherical surfaces, the aspherical amount of the aspherical surface is Δ
When ASPH is set, 0.02> | ΔASPH / L |> 1.0 × 10 ⁻⁶ (3) is satisfied, and the aspherical surfaces of at least two surfaces are mutually arranged from the center of the surface to the peripheral portion. The local curvature power change has two aspherical surfaces having regions of opposite signs, and the two aspherical surfaces are
The first lens group has two surfaces, or the first lens group and
One surface for each of the second lens groups, or the second lens group
It is characterized by being placed in .

According to a second aspect of the present invention, in the first aspect of the invention, the at least two aspherical surfaces are the first on the object side.
It is characterized by being located between the lens surface and the diaphragm position.

A projection optical system according to a third aspect of the present invention is a projection optical system for projecting an image of an object on an image plane, wherein the projection optical system has, in order from the object side, a first lens unit L1 having a positive refractive power. A second lens group L2 having a negative refractive power, a third lens group L3 having a positive refractive power, a fourth lens group L4 having a negative refractive power, and a fifth lens having a positive refractive power. It is provided with a group L5, a sixth lens group L6 having a negative refracting power, and a lens group L7 having a positive refracting power. The conjugate length of the projection optical system is L, and the total power of the negative lens groups is φo
Then, 70> | L × φo |> 17 (φo = Σφoi; φoi is the power of the i-th negative group) (1), and the height of the axial marginal ray is h, and the most off-axis principal ray is When the height of the light ray is hb, in the second lens group, there are a plurality of aspherical surfaces satisfying 15> | hb / h |> 0.35 (2) When the amount of aspherical surface of the aspherical surface is ΔASPH, 0.02> | ΔASPH / L |> 1.0 × 10 ⁻⁶ (3) is satisfied, and at least one of the plurality of aspherical surfaces is satisfied. One aspherical surface is characterized by having a region where the local curvature power gradually increases in the negative direction or gradually decreases in the positive direction from the center to the peripheral portion of the surface.

The invention of claim 4 is characterized in that, in the invention of claim 3, the plurality of aspherical surfaces are between the first lens surface on the object side and the stop position.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, at least one of the aspherical lenses used in the projection optical system is aspherical processed. It is characterized in that the back surface is aspherical.

According to a sixth aspect of the present invention, in any one of the first to fourth aspects of the invention, all of the aspherical lenses used in the projection optical system have the back surface of the aspherical surface processing surface of the aspherical lenses. It is characterized by being an aspherical surface.

According to a seventh aspect of the present invention, in the invention according to any one of the first to fourth aspects, at least one of the aspherical lenses used in the projection optical system is aspherical processed. It is characterized in that the back surface is a flat surface.

According to an eighth aspect of the present invention, in any one of the first to fourth aspects of the invention, all of the aspherical lenses used in the projection optical system have a back surface of the aspherical surface to be processed. It is characterized by being a plane.

According to a ninth aspect of the projection exposure apparatus of the present invention, the pattern on the first object illuminated by the light from the laser light source using the projection optical system according to any one of the first to second aspects is formed.
It is characterized in that it is projected onto the object and exposed.

A projection exposure apparatus according to a tenth aspect of the present invention uses the projection optical system according to any one of the first to eighth aspects to form a pattern on a first object which is illuminated with light from a laser light source to form a second pattern. Exposing both the first object and the second object onto the object by scanning in synchronization with the optical axis of the projection optical system in a direction perpendicular to the optical axis of the projection optical system at a speed ratio corresponding to the projection magnification; It has a feature.

According to the eleventh aspect of the present invention, in the device manufacturing method, the projection optical system according to any one of the first to eighth aspects is used to project and expose a pattern on a reticle onto a wafer surface, and then develop the wafer. It is characterized in that the device is manufactured through processing steps.

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

1 is a lens cross-sectional view of a numerical example 1 of a projection optical system of the present invention, and FIG. 2 is a diagram showing a change of a local curvature power of an aspherical surface of a numerical example 1 of the projection optical system of the present invention. FIG. 3 is an aberration diagram of Numerical Example 1 of the projection optical system of the present invention.

FIG. 4 is a numerical example 2 of the projection optical system of the present invention.
5 is an explanatory diagram of a change in local curvature power of an aspherical surface of Numerical Example 2 of the projection optical system of the present invention, and FIG. 6 is an aberration diagram of Numerical Example 2 of the projection optical system of the present invention. is there.

FIG. 7 is a numerical example 3 of the projection optical system of the present invention.
8 is an explanatory view of a change in local curvature power of an aspherical surface of Numerical Example 3 of the projection optical system of the present invention, and FIG. 9 is an aberration diagram of Numerical Example 3 of the projection optical system of the present invention. is there.

FIG. 10 is a lens cross-sectional view of Numerical Example 4 of the projection optical system of the present invention, and FIG. 11 is an explanatory view of the local curvature power change of the aspherical surface of Numerical Example 4 of the projection optical system of the present invention. 12 is an aberration diagram of Numerical example 4 of the projection optical system of the present invention.

FIG. 13 is a lens cross-sectional view of Numerical Example 5 of the projection optical system of the present invention, and FIG. 14 is an explanatory view of a change in the local curvature power of the aspherical surface of Numerical Example 5 of the projection optical system of the present invention. 15 is an aberration diagram of Numerical example 5 of the projection optical system of the present invention.

FIG. 16 is a lens cross-sectional view of Numerical Embodiment 6 of the projection optical system of the present invention, and FIG. 17 is an explanatory view of the local curvature power change of the aspherical surface of Numerical Embodiment 6 of the projection optical system of the present invention. 18 is an aberration diagram of Numerical example 6 of the projection optical system of the present invention.

FIG. 19 is a lens cross-sectional view of Numerical Embodiment 7 of the projection optical system of the present invention, and FIG. 20 is an explanatory view of a change in local curvature power of an aspherical surface of Numerical Embodiment 7 of the projection optical system of the present invention. 21 is an aberration diagram of Numerical Example 7 of the projection optical system of the present invention.

FIG. 22 shows a paraxial refractive power arrangement of the projection optical system of the present invention. In the sectional view of the lens, PL is a projection optical system. Li is the i-th lens group (i-th group) counted from the object side (the conjugate side with a long distance). The L1 group is a first group having a positive refractive power, the L2 is a second group having a negative refractive power, and the L3 is a third group having a positive refractive power. L4 is the fourth group of negative refractive power, L
5 is a fifth group of positive refractive power, L6 is a sixth group of negative refractive power,
L7 is a seventh unit having a positive refractive power. IP is the image plane,
When used in a projection exposure apparatus, it corresponds to the wafer surface.
The diaphragm is arranged in the sixth group or in the vicinity thereof.

The projection optical system of the present invention has, in order from the object side, a first lens unit L1 having a positive refractive power, a second lens unit L2 having a negative refractive power, and a third lens unit L3 having a positive refractive power. , A fourth lens unit L4 having a negative refractive power, a fifth lens unit L5 having a positive refractive power, a sixth lens unit L5 having a negative refractive power
A lens unit L6, a seventh lens unit L7 having a positive refractive power,
It is composed of seven lens groups, and an appropriate surface is aspherical to obtain good optical performance.

The projection optical system of the present invention has three lens groups having negative refracting power. By distributing the strong negative refractive power in the optical system to the three lens groups, it is possible to satisfactorily correct the Petzval sum, and at the same time, it is possible to achieve an optical system having a short total length. However, in order to have seven lens groups having different refracting power alternately and to configure all with spherical lenses to satisfactorily correct various performances, the number of constituent lenses becomes inevitably large.

Therefore, in the refractive power configuration of the optical system shown in FIG. 16, in order to achieve an optical system having a high numerical aperture and excellent aberration correction without excessively increasing the number of components, An aspherical surface satisfying conditional expression ( 3 ) is introduced into at least one surface of

Conditional expression ( 3 ) is a condition for effectively utilizing the aspherical surface, and at least one aspherical surface satisfying this conditional expression is introduced so that the effect of the aspherical surface is sufficiently exerted. Corrects aberrations well.

If the lower limit of conditional expression ( 3 ) is not satisfied, it will be difficult to correct various aberrations unless the number of constituent elements is increased. This aspherical amount ΔASPH is the object-image distance of 1000.
mm and the wavelength used is 193 nm, ΔASPH = 0.001 mm from the conditional expression ( 3 ), which corresponds to about 10 Newton rings. This is an amount that can exert its effect as an aspherical surface used in a projection exposure system.

Further, in the present invention, in order to bring out the effect of the aspherical surface more remarkably, it is preferable to set the numerical values of the lower limit values of the conditional expression ( 3 ) as follows.

1.0 × 10 ^-5 <| ΔASPH / L | Further, in FIG. 16, from the first lens surface on the object side to the diaphragm surface, the first lens unit L1 having a positive refractive power, the negative refractive power Second lens unit L2 having power, third lens unit L3 having positive refracting power, fourth lens unit L4 having negative refracting power, fifth lens unit L5 having positive refracting power, negative refracting power And a sixth lens unit L6 having

In this range near the object, the height of the off-axis chief ray is high and the on-axis luminous flux is low. Also, near the aperture,
The height of the off-axis chief ray is low, and the on-axis light flux is higher than near the object plane.

Therefore, before the stop, the relationship between the height of the chief ray and the height of the axial luminous flux has changed significantly. In particular, achieving a higher numerical aperture means that the NA luminous flux becomes wider near the object.

Therefore, especially before the stop, the distortion aberration,
It is necessary to minimize the occurrence of off-axis aberrations such as astigmatism and coma. If this is not achieved, the on-axis aberration and the off-axis aberration cannot be balanced, and it becomes very difficult to correct the aberration of the optical system. Therefore, it is more preferable to introduce at least one aspherical surface into this range.
According to this, mainly off-axis aberrations such as distortion, astigmatism, and coma can be effectively corrected.

The diaphragm may be arranged in the sixth lens unit L6 or in the vicinity of L6, or in the fifth lens unit L5 or in the vicinity of L5.

More preferably, the present invention is characterized in that at least one aspherical surface is provided between the first lens surface on the object side and the diaphragm position.

[0067]

Conventionally, in a reduction type projection optical system,
It was very difficult to satisfactorily correct distortion aberration, field curvature, astigmatism, as well as meridional and sagittal lateral aberrations while maintaining telecentricity.

The telecentricity, the distortion, the field curvature, and the astigmatism are all aberration amounts related to the principal ray passing through the center of the light flux, and those aberrations and the like are for an object having a high principal ray height throughout the entire lens system. It depends on the lens arrangement on the side and the lens shape. This is to refract the same principal ray so as to correct distortion, field curvature, and astigmatism while maintaining telecentricity for the principal rays from all object points on the object. Because it was difficult.

Since the lower ray of the meridional on the lens is refracted at a position higher than the principal ray, it is difficult to balance the lateral aberration of the meridional and the aberration of the principal rays. At the same time, when trying to correct the field curvature that tends to be under-corrected as the image height normally increases, the concave lens strongly refracts, but this time the peripheral portion of the lateral aberration of the sagittal with a high image height changes further over. This makes it difficult to achieve good balance.

In such a situation, increasing the NA and ensuring a wide exposure area means further expansion of the light flux on the object side and the image height,
The difficulty of aberration correction is amplified.

Therefore, in the present invention, the surface that greatly affects the off-axis chief ray that satisfies the conditional expression (2) is an aspherical surface. By effectively correcting the above-mentioned aberration to be improved by the aspherical surface, the burden of other aberration correction is reduced, and good optical performance is realized.

When the value goes below this lower limit, the influence on the axial marginal ray becomes larger than that on the off-axis chief ray, so that the effect of correcting the above-mentioned aberration to be improved is reduced, and the high NA is increased.
And it becomes difficult to secure a large exposure area.

In FIG. 16, the condition (2) is satisfied in the range from the object plane to the lens groups L1 to L4. By introducing at least one aspherical surface into the surface in such a range, good optical performance can be realized.

Particularly, when an aspherical surface is applied to the lens unit L1, the height hb of the off-axis chief ray is the highest, which is effective mainly for controlling the distortion aberration.

Next, when an aspherical surface is applied to the negative lens unit L2,
Although it is mainly effective for controlling field curvature and astigmatism, it is also effective for controlling distortion because it has a canceling relationship with the positive lens unit L1. The positive lens group L3 has a high axial ray field height h and a large contribution to spherical aberration and coma. Therefore, an aspherical surface should be introduced to correct spherical aberration and coma.

[0077]

Generally, when the object-image distance L becomes long, the power φo of the lens group of each refracting power also becomes small, and conversely, when the object-image distance L becomes short, the power φo of the negative lens group becomes large. In the invention, by setting the product of conditional expression (1) to be 17 or more, the power of the negative lens group is set to be large, and mainly the field curvature and astigmatism are favorably corrected. When the value goes below the lower limit, the Petzval sum increases in the positive direction, making it difficult to satisfactorily correct field curvature and astigmatism.

[0079]

For example, if the upper limit of conditional expression ( 3 ) is exceeded, the aspherical surface amount becomes too large, and the processing time of the lens increases. In addition, the high-order aberration generated on the aspherical surface becomes large, which may make it difficult to satisfactorily correct aberrations.

If the upper limit of conditional expression ( 2 ) is exceeded, the working distance cannot be secured because the lens is too close to the object plane. If the projection optical system has an extremely small magnification,
The working distance may be secured even if the above conditional expression is exceeded, but such an optical system having an extremely small magnification is not practical for lithography.

If the upper limit of conditional expression ( 1 ) is exceeded, the power of the negative lens group having negative refracting power becomes too large, and the Petzval sum is overcorrected, and mainly field curvature and astigmatism are corrected well. Becomes difficult.

Further, the lens diameter of the positive lens group having a positive refracting power becomes large, and the number of lenses increases.

In the present invention, more preferably, at least one of the aspherical surface introduction methods should specifically satisfy the following conditions. According to this, it becomes possible to increase the effect of the aspherical surface and achieve good aberration correction.

Condition (a): The aspherical surface should have at least two aspherical surfaces having regions of opposite signs of changes in local curvature power from the center to the peripheral portion of the surface.

Condition (b): Among the aspherical surfaces, at least one aspherical surface in the concave group (lens group having a negative refractive power) has a local curvature power gradually increasing in the negative direction from the center of the surface to the peripheral portion. Having areas that become stronger or weaker in the positive direction.

Condition (c): Among the aspherical surfaces, at least one aspherical surface in the convex group (lens group having a positive refractive power) has a local curvature power gradually increasing in the positive direction from the center of the surface to the peripheral portion. It has an area that becomes gradually weaker in the negative or negative direction.

Generally, there are two ways of thinking when performing aberration correction using an aspherical surface. One is a method of introducing an aspherical surface so as to reduce the occurrence of aberration on the corresponding surface (auxiliary introduction), and the other is a method of introducing an aspherical surface so as to cancel the aberration in relation to other surfaces. (Active introduction). The present invention basically adopts the latter concept of positive introduction to skillfully correct aberrations.

By making the local power canceling relations of the two aspherical surfaces so as to satisfy the above condition (a), it becomes easy to give a refractive power change that minimizes a plurality of aberrations at the same time. Become. In particular, high-order aberration correction that is difficult to correct, for example, distortion aberration, field curvature, astigmatism, sagittal lateral aberration, and meridional lateral aberration in the higher-order region are favorably corrected under this condition (a).

More preferably, two aspherical surfaces satisfying the condition (a) are arranged in either the lens group L1 or the lens group L2, or, of the two aspherical surfaces, the lens group L1 and the lens are It is desirable to arrange at least one sheet in each of the groups L2 in order to achieve better performance. By introducing an aspherical surface satisfying the above conditions into the lens unit L1 or L2, or the lens unit L1 and L2, it becomes possible to effectively correct mainly the distortion and the image plane.

Satisfying the condition (b) is particularly effective mainly for correction of field curvature, meridional and sagittal lateral aberration. Even if the Petzval sum is corrected well, it is difficult to correct the field curvature of a high image height, especially the sagittal field curvature that falls to the under side, and it is difficult to balance with the meridional or sagittal lateral aberration as described above. is there.

Therefore, in the present invention, by introducing an aspherical surface so as to satisfy the condition (b), the power in the negative refractive power direction in the peripheral portion from the optical axis is increased without excessively increasing the paraxial power. It will have a larger area. As a result, it is possible to correct the under portion of the field curvature to the over side, and as a result, increase the degree of freedom in aberration correction of surfaces other than the aspherical surface, and correct meridional, sagittal lateral aberration, distortion, etc. It becomes possible to perform well.

More preferably, one or more aspherical surfaces satisfying the condition (b) are arranged in the lens unit L1 or the lens unit L2 in order to achieve better performance. By introducing an aspherical surface satisfying the above conditions into the lens unit L1 or L2, or the lens unit L1 and L2, it becomes possible to effectively correct mainly the distortion and the image plane.

It is desirable to improve the performance further by having an aspherical surface having a region where the local curvature power gradually increases in the positive direction from the center of the surface to the peripheral portion as in the condition (c).

Such an aspherical surface is effective mainly for correcting object-side telecentricity and high-order distortion. In the present invention, the power of the three negative lens groups in the lens system having the seven-group structure can be strengthened to correct the field curvature and astigmatism related to the Petzval sum, but the negative power has an effect. Since the balance of the object-side telecentricity is lost, and at the same time high-order under distortion is generated, the balance of the object-side telecentricity is restored to good, and at the same time, the opposite over-distortion is generated and canceled. It is desirable to make the correction good.

Therefore, by having an aspherical surface satisfying at least one of the conditions (a) and (b), it becomes possible to obtain an optical system having high resolution and excellent aberration correction. Further, having an aspherical surface that satisfies the condition (c) is also effective in realizing an optical system with better performance.

If a plurality of aspherical surfaces are introduced in addition to the above aspherical surfaces, it becomes possible to perform better aberration correction over the entire surface. An aspherical surface having a region in which the local curvature power is weakened in the positive direction from the center of the surface to the peripheral portion is introduced into the group having a high positive power of the axial marginal ray, that is, the lens group L5 and the lens group L7. By doing so, it becomes possible to satisfactorily correct spherical aberration and coma.

The back surface (opposite surface) of the processed surface of the aspherical surface of the aspherical lens need not be a spherical surface. For example,
When the back surface of the aspherical surface is a flat surface, it becomes easier to adjust the aspherical element during processing and assembly. In particular,
This is effective when a lens having a large effective diameter is aspherical. Note that, of all aspherical lenses used in the projection optical system, the back surface of such an aspherical surface may be used as a flat surface for some of them. Further, the back surfaces of the aspherical surface processing surfaces of all the aspherical lenses in the projection optical system may be flat surfaces.

Furthermore, the back surface of the aspherical surface processed surface may be aspherical surface processed. That is, it is possible to use a double-sided aspherical lens. Also in this case, all the aspherical lenses in the projection optical system may be double-sided aspherical lenses, or some of the aspherical lenses may be double-sided aspherical lenses.

Next, an example of the aspherical surface processing method will be described below. As an example of a method for processing an aspherical lens corresponding to a large-diameter lens used in lithography or the like, as an example thereof, for example, a document “Robert A. Jones;
led polishing of telescope mirror segments, "OPTI
CAL ENGINEERING, Mar / Apr Vol.22, No.2, 1983 ", etc., a machining method is reported. That is, a method of forming an aspherical surface shape by a three-dimensional computer-controlled grinding machine and then polishing by a computer-controlled grinding machine (CCP) has a shape accuracy of 0.025 λrms (λ =
633 nm) has been obtained.

Here, FIG. 23 is a schematic view showing a processing method by mechanical processing of an aspherical surface. In the figure, 501 is a substrate, 5
Reference numeral 02 is a substrate rotating mechanism, 503 is a stage, 504 is a spherical pad, 505 is a spherical pad rotating mechanism, 506 is a load control mechanism, 507 is a polishing liquid supply nozzle, and 508 is a polishing liquid.

The substrate 501 rotatably attached to the movable stage 503 is rotated by the substrate rotating mechanism 502. The contact pressure is controlled by the load control mechanism 506 on the surface of the rotating substrate 501, the rotating spherical pad 504 is contacted by the spherical pad rotating mechanism 505, and the polishing liquid 508 is supplied to the contact surface from the polishing liquid supply nozzle 507. The contact surface is polished by.

The position of the stage 503 and the load control mechanism 50
The contact pressure of the spherical pad 504 applied by 6 is controlled by a computer (not shown).

The method for processing the aspherical surface is not limited to the above-mentioned methods, and other methods may be used.

Next, the features of the lens configuration of the numerical embodiments of the present invention will be described. In each of the numerical examples, the object side (reticle side) and the image plane side (wafer side) are substantially telecentric. The projection magnification is 1/4, the image-side numerical aperture is NA = 0.65, and the object-image distance (first object plane to second object plane) is L = 1000 mm. The reference wavelength is 193 nm, and the screen area has a diameter of the exposure area on the wafer of 27.3 mm.

2, FIG. 5, FIG. 8, FIG. 11, FIG. 14, and FIG.
7. The vertical axis in FIG. 20 normalizes the height of the aspherical surface from the optical axis by the effective diameter. The horizontal axis represents the aspherical surface number, and the left and right directions in the respective graphs indicate the negative and positive directions of the change in the local curvature power.

In Numerical Embodiment 1 of FIG. 1, in order from the object side,
The first lens unit L1 having a positive refractive power, the second lens unit L2 having a negative refractive power, the third lens unit L3 having a positive refractive power, the fourth lens unit L4 having a negative refractive power, Fifth lens group L5 having a refractive power, sixth lens group L6 having a negative refractive power, seventh lens group L having a positive refractive power
It is composed of 7.

Seven aspherical surfaces are used in the optical system, and Table 1 shows values corresponding to the conditional expressions (1), (2), and (3). Further, an aberration diagram is shown in FIG. 3, and a change in local curvature power of the aspherical surface is shown in FIG.

A specific lens configuration will be described below. The first lens unit L1 is composed of one plano-convex aspherical positive lens whose convex surface faces the image side. The aspherical surface of r2 has a region where the change of the local curvature power is in the positive direction,
The operation of the above-mentioned condition (c) is satisfied. This aspherical surface mainly produces positive distortion, which contributes to correction of distortion.

The second lens unit L2 is composed of one biconcave aspherical negative lens. The aspherical surface of r3 has a region in which the change of the local curvature power is in the negative direction, and satisfies the operation of the condition (b). Further, in relation to r2 of the lens unit L1, the local curvature power change has a region in the opposite direction, and the action of the condition (a) is also satisfied.

The third lens unit L3 is composed of, in order from the object side, a plano-convex positive lens having a convex surface directed toward the image side, and a substantially plano-convex aspherical positive lens having a convex surface directed toward the object side.

The fourth lens unit L4 is composed of, in order from the object side, a biconcave negative lens and a biconcave aspherical negative lens. The aspherical surface of r11 has a region in which the change of the local curvature power is in the negative direction, and satisfies the effect of (b).
Further, in relation to the r2 of the lens unit L1, the local curvature power change has a region in the opposite direction, and the effect of (a) is also satisfied. This aspherical surface mainly contributes to the well-balanced correction of the image plane, coma, and the like.

The fifth lens unit L5 is composed of, in order from the object side, a substantially plano-convex positive lens having a convex surface directed toward the image side, and a biconvex positive lens.

The sixth lens unit L6 is composed of one biconcave aspherical negative lens. This aspherical surface effectively corrects spherical aberration and coma that are mainly caused by a strong negative refractive power.

The seventh lens unit L7 includes, in order from the object side, a positive meniscus lens having a convex surface directed toward the image side, a biconvex aspherical positive lens, and a substantially plano-convex positive lens having a convex surface directed toward the object side. A lens, two meniscus-shaped positive lenses having a convex surface facing the object side, a meniscus-shaped negative lens having a concave surface facing the image side, and a meniscus-shaped positive lens having a convex surface facing the object side. In the seventh lens group, the aspherical surface used at a position where the axial light flux, which is a light flux emitted from the axis on the object plane, is mainly used in the seventh lens group having a strong positive refractive power. It is used to correct the negative spherical aberration that occurs. Further, the aspherical surface used on the convex surface near the image surface mainly contributes to the well-balanced correction of coma and distortion.

As described above, by introducing at least one aspherical surface satisfying the conditional expression ( 3 ) into the optical system, the effect of the aspherical surface is sufficient to achieve the optical system having a high numerical aperture. Is being demonstrated.

In particular, by introducing an aspherical lens having five surfaces before the diaphragm, mainly distortion, astigmatism, coma and the like can be effectively corrected in a well-balanced manner. Further, by introducing an aspherical surface into the surface that satisfies the conditional expression (2), the surface that greatly affects the off-axis chief ray is set as an aspherical surface, and aberrations related to off-axis are mainly corrected and It reduces the burden of aberration correction and realizes good optical performance.

In this embodiment, the aspherical surfaces that satisfy the conditional expression (2) are the r2, r3, r7, and r11 surfaces. Further, by introducing an aspherical surface that satisfies at least one of the above-mentioned conditions (a) and (b), it becomes possible to increase the effect of the aspherical surface and achieve good aberration correction. .

In this embodiment, seven aspherical lenses are used to achieve a total of 16 optical systems with a high numerical aperture (high NA). In addition, the present embodiment includes an aspherical lens whose back surface of the aspherical surface is a flat surface.

In Numerical Example 2 of FIG. 4, seven aspherical surfaces are used in the optical system, and conditional expression (1),
Table 2 shows the values corresponding to (2) and (3). Further, FIG. 6 shows an aberration diagram, and FIG. 5 shows a change in local curvature power of the aspherical surface.

A specific lens configuration will be described below. The first lens unit L1 is composed of one plano-convex aspherical positive lens whose convex surface faces the image side. The aspherical surface of r2 has a region where the change of the local curvature power is in the positive direction, and satisfies the operation of the above-mentioned condition (c).

The second lens unit L2 is composed of one biconcave aspherical negative lens. The aspherical surface of r3 has a region in which the change of the local curvature power is in the negative direction, and satisfies the operation of the condition (b). Further, in relation to r2 of the lens unit L1, the local curvature power change has a region in the opposite direction, and the action of the condition (a) is also satisfied.

The third lens unit L3 is composed of, in order from the object side, a plano-convex positive lens having a convex surface directed toward the image side, and a substantially plano-convex aspherical positive lens having a convex surface directed toward the object side.

The fourth lens unit L4 is composed of, in order from the object side, a biconcave negative lens and a biconcave aspherical negative lens.

The fifth lens unit L5 is composed of three biconvex positive lenses.

The sixth lens unit L6 is composed of one biconcave aspherical negative lens.

The seventh lens unit L7 includes, in order from the object side, a meniscus positive lens having a convex surface directed toward the image side, a biconvex aspherical positive lens, and a substantially plano-convex positive lens having a convex surface directed toward the object side. It includes a lens, two meniscus-shaped positive lenses having a convex surface facing the object side, a meniscus-shaped negative lens having a concave surface facing the image side, and a meniscus-shaped aspherical positive lens having a convex surface facing the object side.

In this embodiment, seven aspherical lenses are used to achieve a total of 17 optical systems with a high numerical aperture (high NA).

Table 3 shows values corresponding to the conditional expressions (1), (2) and (3) in the numerical value example 3 of FIG.
Further, FIG. 9 shows aberration diagrams, and FIG. 8 shows changes in local curvature power of the aspherical surface. Eight aspherical surfaces are used. In all the aspherical lenses in this embodiment, the back surface of the aspherical surface is flat.

A specific lens configuration will be described below. The first lens unit L1 is composed of, in order from the object side, a plano-convex aspherical positive lens having a convex surface facing the image side, and a biconvex positive lens. The aspherical surface of r2 has a region where the change of the local curvature power is in the positive direction, and satisfies the operation of the above-mentioned condition (c).

The second lens unit L2 is composed of, in order from the object side, a biconcave negative lens and an aspherical negative lens having a concave surface facing the image side. The aspherical surface of r8 has a region in which the change in local curvature power is in the negative direction, and satisfies the action of the condition (b). Further, in relation to r2 of the lens unit L1, the local curvature power change has a region in the opposite direction, and the action of the condition (a) is also satisfied.

The third lens unit L3 is composed of, in order from the object side, a plano-convex aspherical positive lens having a convex surface facing the image side, and a biconvex positive lens. The aspherical surface of r10 has a region in which the change of the local curvature power is in the positive direction, and satisfies the operation of the above-mentioned condition (c). In relation to r8 of the lens unit L2, the change of the local curvature power has a region in the opposite direction, and the action of the above-mentioned condition (a) is also satisfied.

The fourth lens unit L4 includes a biconcave negative lens, a plano-concave aspherical negative lens having a concave surface facing the object side,
Consists of. The aspherical surface of r15 has a region in which the change in local curvature power is in the negative direction, satisfies the condition (b), and is positive in the peripheral portion, and the divergence of this group itself The effects are canceled out at a higher order.

The fifth lens unit L5 has, in order from the object side, a plano-convex aspherical positive lens having a convex surface directed toward the image side, a biconvex positive lens, and a substantially plano-convex shape having a convex surface directed toward the object side. It consists of an aspherical positive lens.

The sixth lens unit L6 is composed of, in order from the object side, a biconcave negative lens and a plano-concave aspherical negative lens having a concave surface facing the object side.

The seventh lens unit L7 includes, in order from the object side, a plano-convex positive lens having a convex surface directed toward the image side, a plano-convex aspherical positive lens having a convex surface directed toward the image side, and a biconvex positive lens. lens,
Plano-convex positive lens with convex surface facing the object side, meniscus-shaped positive lens with concave surface facing the image side, meniscus-shaped negative lens with concave surface facing the image side, plano-convex shape with convex surface facing the object side It consists of an aspherical positive lens.

By making the back surface of the aspherical surface of the aspherical lens flat as in the present embodiment, an optical system that can be easily processed and adjusted can be achieved.

In this embodiment, eight aspherical lenses are used to achieve a total of 20 optical systems with a high numerical aperture (high NA).

Table 4 shows values corresponding to the conditional expressions (1), (2) and (3) in the numerical example 4 of FIG.
Further, FIG. 12 shows aberration diagrams, and FIG. 11 shows changes in local curvature power of the aspherical surface. Eight aspherical surfaces are used in the optical system, and Table 4 shows values corresponding to the conditional expression ( 3 ).

In this embodiment as well, as in Numerical Embodiment 3, all the aspherical lenses have a flat back surface as the aspherical surface.

A specific lens configuration will be described below. The first lens unit L1 includes, in order from the object side, a plano-convex aspherical positive lens having a convex surface facing the image side, and a biconvex positive lens. The aspherical surface of r2 has a region in which the change in local curvature power is in the negative direction.

The second lens unit L2 is composed of two plano-concave aspherical negative lenses with the concave surface facing the image side, in order from the object side. The aspherical surfaces of r4 and r6 have a region in which the local curvature power changes in the positive direction. Also, r of the lens unit L1
In relation to 2, both r4 and r6 have a region in which the local curvature power changes in the opposite direction, which satisfies the effect of the condition (a).

The third lens unit L3 is composed of, in order from the object side, a plano-convex aspherical positive lens having a convex surface directed toward the image side, and a biconvex positive lens. The aspherical surface of r10 has a region in which the change of the local curvature power is in the positive direction, and satisfies the operation of the above-mentioned condition (c).

The fourth lens unit L4 includes, in order from the object side, a meniscus negative lens having a concave surface facing the image side, a biconcave negative lens, and a plano-concave aspherical negative lens having a concave surface facing the object side. , Consists of. The aspherical surface of r17 has a region in which the change of the local curvature power is in the negative direction, and satisfies the operation of the above-mentioned condition (b). Also, r1 of the lens unit L3
In the relationship with 0, the change of the local curvature power has a region in the opposite direction, which satisfies the effect of the condition (a).

The fifth lens unit L5 is, in order from the object side, a meniscus positive lens having a concave surface facing the object side, a biconvex positive lens, and a plano-convex aspherical positive lens having a convex surface facing the object side. , Consists of.

The sixth lens unit L6 is composed of two biconcave negative lenses.

The seventh lens unit L7 includes, in order from the object side, a plano-convex aspherical positive lens having a convex surface directed toward the image side, two biconvex positive lenses, and a meniscus shape having a concave surface directed toward the image side. No. 1 positive lens, and a plano-convex aspherical positive lens having a convex surface facing the object side.

In this embodiment, eight aspherical surfaces are used to achieve a total of 19 optical systems with a high numerical aperture (high NA).

Table 5 shows values corresponding to the conditional expressions (1), (2) and (3) in the numerical value example 5 of FIG.
Further, FIG. 15 shows aberration diagrams, and FIG. 14 shows changes in the local curvature power of the aspherical surface. Eight aspherical surfaces are used in the optical system. In this embodiment, all the aspherical lenses have an aspherical surface on the back surface of the aspherical surface. That is, four double-sided aspherical lenses are used.

A specific lens configuration will be described below. The first lens unit L1 is composed of one biconvex double-sided aspherical positive lens. The double-sided aspherical surfaces of r1 and r2 have a region in which the local curvature power changes have opposite signs so as to cancel each other out, satisfying the above-mentioned condition (a), and at the same time satisfying the condition (c). Is satisfied, and the power change in the positive direction remains as a total.

The second lens unit L2 is composed of one biconcave double-sided aspherical negative lens. The double-sided aspherical surfaces of r3 and r4 have areas where the changes in the local curvature powers have opposite signs so as to cancel each other out in the peripheral portion.
Although the operation of (b) is satisfied, the power change in the negative direction remains as a total.

Here, the relationship between the aspherical surfaces of the lens unit L1 and the lens unit L2 is also a canceling relationship. Therefore, the action of the condition (c) is satisfied.

The third lens unit L3 is composed of, in order from the object side, a plano-convex positive lens having a convex surface facing the image side, and a biconvex positive lens. It is effective for correcting lateral aberrations of meridional and sagittal.

The fourth lens unit L4 is composed of, in order from the object side, a biconcave aspherical negative lens and a biconcave negative lens. The aspherical surfaces on both sides of r9 and r10 have a slight canceling relationship at the outermost peripheral portion, but the power change in the positive direction remains as a total, and correction is made so as to cancel the diverging action of this group itself.

The fifth lens unit L5 is composed of, in order from the object side, two biconvex positive lenses.

The sixth lens unit L6 is composed of, in order from the object side, two biconcave negative lenses.

The seventh lens unit L7 includes, in order from the object side, three biconvex positive lenses, two meniscus positive lenses having concave surfaces facing the image side, and a meniscus shape having concave surfaces facing the image side. Negative lens, and a positive meniscus aspherical lens with a convex surface facing the object side.

By using these double-sided aspherical lenses, there are the advantages that the degree of freedom in design is increased, better aberration correction is possible, and the number of elements of the aspherical lens itself is small.

In this embodiment, a double-sided aspherical lens is used.
1 sheet in total with a high numerical aperture (high NA)
Achieved 7 optical systems.

In this embodiment, the first, second, fourth,
An example in which a double-sided aspherical surface is introduced into the seven lens group has been shown, but the invention is not limited to this. That is, it may be introduced into the other 3, 5, and 6 lens groups, or the number of double-sided aspherical lenses may be smaller than that in this embodiment. Further, an aspherical lens whose aspherical surface is a flat back surface and an aspherical lens whose aspherical surface is a spherical surface may be mixed and used.

Table 6 shows values corresponding to the conditional expressions (1), (2) and (3) in the numerical value example 6 of FIG.
Further, FIG. 18 shows aberration diagrams, and FIG. 17 shows changes in local curvature power of the aspherical surface.

In this embodiment, nine aspherical surfaces are used. In addition, a total of 6 aspherical lenses (3 aspherical lenses on both sides and 3 aspherical lenses whose back surface is aspherical) are used (the number of aspherical surfaces is 9). .

A specific lens configuration will be described below. The first lens unit L1 includes, in order from the object side, a substantially plano-convex positive lens having a convex surface directed toward the image side, a biconvex aspherical positive lens,
Consists of. The aspherical surface of r3 has a region in which the change in local curvature power is in the positive direction, and satisfies the action of the above-mentioned condition (c).

The second lens unit L2 is composed of, in order from the object side, a biconcave double-sided aspherical negative lens and a biconcave negative lens. The aspherical surfaces of r5 and 6 have a region in which the change of the local curvature power is in the negative direction, and satisfy the operation of the above-mentioned condition (b). Further, the r3 aspherical surface of the lens unit L1 has a region in which the changes in the local curvature powers have opposite signs so as to cancel each other out, and the above-mentioned condition (a) is satisfied. Further, even in the case of r5 and r6, the changes in the local curvature powers have opposite signs so as to cancel each other in the peripheral portion.

The third lens unit L3 is composed of, in order from the object side, a meniscus-shaped positive lens having a concave surface facing the object side, and a biconvex aspherical positive lens. The aspherical surface of r11 has a region in which the change in local curvature power is in the positive direction, and satisfies the effect of the above-mentioned condition (c).

The fourth lens unit L4 comprises, in order from the object side, a meniscus negative lens having a concave surface facing the image side, and two biconcave negative lenses.

The fifth lens unit L5 includes, in order from the object side, a substantially plano-convex positive lens having a convex surface directed toward the image side, a biconvex aspherical positive lens, and a substantially plano-convex shape having a convex surface directed toward the object side. Consisting of a positive lens.

The sixth lens unit L6 is composed of, in order from the object side, a substantially plano-convex negative lens having a concave surface facing the image side, and a biconcave negative lens.

The seventh lens unit L7 includes, in order from the object side, a biconvex positive lens, a biconvex double-sided aspherical positive lens, two meniscus positive lenses having a concave surface facing the image side, and an image side. It consists of a meniscus double-sided aspherical positive lens with the concave surface facing to.

In this embodiment, a double-sided aspherical lens is used.
3 aspherical lenses whose back surface is aspherical
1 sheet in total with a high numerical aperture (high NA)
Achieved 9 optical systems.

Table 7 shows values corresponding to the conditional expressions (1), (2) and (3) in the numerical value example 7 of FIG.
Further, FIG. 21 shows aberration diagrams, and FIG. 20 shows changes in the local curvature power of the aspherical surface. In this embodiment, four aspherical surfaces are used.

A specific lens configuration will be described below. The first lens unit L1 is composed of, in order from the object side, a meniscus positive lens having a concave surface facing the object side, and a biconvex aspherical positive lens. In the aspherical surface of r3, the change of the local curvature power is in the negative direction, which cancels the converging action of this group itself.

The second lens unit L2 is composed of, in order from the object side, a meniscus negative lens having a concave surface facing the image side, a biconcave aspherical negative lens, and a biconcave negative lens. r
In the aspherical surface of No. 8, the change of the local curvature power is in the negative direction at the central portion, and the action of the condition (b) is satisfied. In addition, the peripheral portion is in the positive direction, and the divergence action of this group itself is canceled at a high order. Further, in the peripheral portion, the change of the local curvature power is in the opposite direction in relation to r3 of the first group, and the action of the condition (c) is also satisfied.

The third lens unit L3 is composed of, in order from the object side, a positive lens having a convex surface directed toward the image side, and a biconvex aspherical positive lens. In the aspherical surface of r13, the change of the local curvature power is in the positive direction in the central part and satisfies the action of the condition (a), and in the peripheral part, it is in the negative direction, and the converging action of this group is higher. It has been canceled. Further, in the peripheral portion, the change of the local curvature power is in the opposite direction in relation to r8 of L2, and the action of the condition (c) is also satisfied.

The fourth lens unit L4 includes, in order from the object side, a meniscus negative lens having a concave surface facing the image side, and two biconcave negative lenses.

The fifth lens unit L5 is composed of three biconvex positive lenses in order from the object side.

The sixth lens unit L6 is composed of two biconcave negative lenses.

The seventh lens unit L7 includes a meniscus-shaped positive lens whose convex surface faces the image side, two biconvex positive lenses, two meniscus-shaped positive lens whose concave surface faces the image side, and an image It is composed of a substantially plano-concave negative lens having a concave surface facing the side, and an aspherical positive lens having a convex surface facing the object side.

In this embodiment, four aspherical lenses are used. In particular, by using three aspherical surfaces from the object surface to the diaphragm surface, off-axis aberrations are satisfactorily corrected, and at the same time, a total of 21 optical systems are achieved with a high numerical aperture (high NA).

In this embodiment, fluorite is used as the seventh lens unit L.
Although it is used in No. 7, it may be used in other lens groups.

In the above numerical examples, there is an example in which the conical constant k relating to the aspherical surface shape is zero, but the conical constant may be used as a variable for designing.

Further, among the numerical examples, the numerical example 7
Except for the above, a quartz lens was used as the glass material, but fluorite may be used. That is, by using both fluorite and quartz, it becomes possible to correct chromatic aberration to a smaller extent. Further, it may be composed of only fluorite.

An aspherical surface may be further added in order to further improve the image forming performance. In particular, adding an aspherical surface that satisfies the conditional expression ( 3 ) between the object and the diaphragm makes it possible to more particularly correct distortion, field curvature, and the like. Further, when they are arranged in the group after the stop, it becomes possible to further improve various aberrations such as spherical aberration and coma in particular.

Further, this time, the exposure light source has a wavelength of 248n.
Although the KrF wavelength of m or the ArF wavelength of 193 nm is used, the wavelength may be 250 nm or less. For example, a shorter wavelength F2 laser wavelength or the like may be used.
Moreover, the magnification of the optical system is not limited to 1/4 times as in the present embodiment, and other magnifications may be used.

As described above, by using an aspherical surface, the number of lenses is greatly reduced and a projection optical system having a high numerical aperture is achieved. Further, by making the back surface of the aspherical surface to be a flat surface, it is possible to obtain a projection optical system which can be easily processed and adjusted. If the back surface of the aspherical surface is an aspherical surface, the degree of freedom in design increases, and better aberration correction becomes possible.

The structural specifications of the above-described numerical embodiment will be shown below. In the numerical embodiment, ri is the radius of curvature of the i-th lens surface in order from the object side, di is the i-th lens thickness and air gap in order from the object side, and ni is the glass of the i-th lens in order from the object side. The refractive index of

The shape of the aspherical surface is given by

[0188]

[Equation 1]

Shall be given in. Here, X is the amount of displacement from the lens apex in the optical axis direction, H is the distance from the optical axis, ri is the radius of curvature, k is the conic constant, A ,. ． ． ． , G
Is an aspherical coefficient. The refractive indices of quartz and fluorite for the exposure wavelength of 193 nm are 1.5602 and 1.501, respectively.
40.

Further, the local curvature power PH of the aspherical surface is given by the following expression by using the above-mentioned expression X of the aspherical surface as a function of X (H).

PH = (N′−N) / ρ where ρ = (1 + X ′ ² ) ^3/2 / X ″ N and N ′ are the refractive indices of the medium before and after the refractive surface.

[0192]

[Outer 1]

[0193]

[Outside 2]

[0194]

[Outside 3]

[0195]

[Outside 4]

[0196]

[Outside 5]

[0197]

[Outside 6]

[0198]

[Outside 7]

[0199]

[Table 1]

[0200]

[Table 2]

[0201]

[Table 3]

[0202]

[Table 4]

[0203]

[Table 5]

[0204]

[Table 6]

[0205]

[Table 7]

FIG. 24 is a schematic view of a main part of a semiconductor device manufacturing system using the projection optical system of the present invention. In this embodiment, a semiconductor device is manufactured by printing a circuit pattern provided on a reticle, a photomask or the like onto a wafer (photosensitive substrate, second object). The system roughly includes a projection exposure apparatus, a mask storage apparatus, an original plate inspection apparatus, and a controller, which are arranged in a clean room.

In the figure, 1 is an excimer laser as a light source, and 2 is a united illumination optical system. P. The reticle (mask, first object) 3 set to is illuminated from above with a predetermined NA (numerical aperture). Numeral 909 is, for example, a numerical value example 1 shown in FIG.
Is a projection lens for projecting a circuit pattern (object) formed on the reticle 3 onto the wafer 7 such as a silicon substrate and printing it.

An alignment system 900 aligns the reticle 3 and the wafer 7 prior to the exposure operation.
The alignment system 900 has at least one microscope system for reticle observation. 911 is a wafer stage. The above-mentioned members constitute a projection exposure apparatus.

Reference numeral 914 denotes a mask storage device, which stores a plurality of masks inside. Reference numeral 913 is an inspection device that detects the presence or absence of foreign matter on the mask. This inspection device 91
3 is the exposure position E.3 when the selected mask is pulled out from the storage device 914. P. The foreign matter on the mask is inspected before being set. The controller 918 controls the sequence of the entire system, and controls the operation commands of the storage device 914 and the inspection device 913 as well as the sequence of basic operations of the projection exposure apparatus such as alignment, exposure, and step feed of the wafer.

An embodiment of a method of manufacturing a semiconductor device using this system will be described below.

FIG. 25 shows a device (IC or LS) of the present invention.
6 is a flowchart of a method of manufacturing a semiconductor chip such as I, a liquid crystal panel, a CCD, or the like). This will be described. In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask manufacture), a mask having the designed circuit pattern is manufactured. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask (reticle) 3, wafer 7 and projection lens of the present invention. Step 5
(Assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes a process such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. In step 6 (inspection), the semiconductor device produced in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 26 is a detailed flowchart of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. Step 13 (electrode formation)
Then, electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer.
In step 15 (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the projection lens 909 of the present invention projects and exposes the circuit pattern of the reticle onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), parts other than the developed resist are scraped off. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, it is possible to easily manufacture a highly integrated semiconductor device, which has been difficult to manufacture conventionally.

The projection exposure apparatus of the above embodiment is a projection exposure apparatus that exposes the circuit pattern on the reticle 3 onto the wafer at one time, but instead of this, the light from the laser light source is used as the illumination optical system. A part of the reticle 3 is irradiated via the reticle 3, and the circuit pattern on the reticle 3 is projected onto the wafer 7 by the projection optical system so that both the reticle 3 and the wafer 7 are perpendicular to the optical axis of the projection optical system. It may be a so-called scanning type projection exposure apparatus that scans, projects and exposes according to the projection magnification.

[0215]

As described above, according to the present invention, by effectively using the aspherical surface, the projection optical system which uses a small number of constituent lenses and can secure a high resolution and a wide exposure area, and a projection optical system using the same. The projection exposure apparatus that has been used can be achieved.

In addition to the above, according to the present invention, by effectively using the aspherical surface in the above-mentioned structure, a higher resolution and a wider exposure area can be secured, and the structure is ensured, as compared with the optical system composed of the conventional spherical surface. It is possible to achieve a dual telecentric projection optical system in which the number of sheets is small and a high resolution and a wide exposure area are secured.

Further, according to the projection optical apparatus using the projection optical system of the present invention, it is possible to achieve a device manufacturing method capable of easily manufacturing a highly integrated semiconductor device which has been difficult to manufacture in the past. .

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view of Numerical Example 1 of a projection optical system of the present invention.

FIG. 2 is an explanatory diagram of a local curvature power change of an aspherical surface in Numerical Example 1 of the projection optical system of the present invention.

FIG. 3 is an aberration diagram of Numerical example 1 of the projection optical system of the present invention.

FIG. 4 is a lens sectional view of Numerical Example 2 of the projection optical system of the present invention.

FIG. 5 is an explanatory diagram of a local curvature power change of an aspherical surface in Numerical Example 2 of the projection optical system of the present invention.

FIG. 6 is an aberration diagram of Numerical example 2 of the projection optical system of the present invention.

FIG. 7 is a lens sectional view of Numerical Example 3 of the projection optical system of the present invention.

FIG. 8 is an explanatory diagram of a local curvature power change of an aspherical surface in Numerical Example 3 of the projection optical system of the present invention.

FIG. 9 is an aberration diagram of Numerical example 3 of the projection optical system of the present invention.

FIG. 10 is a lens cross-sectional view of Numerical Example 4 of the projection optical system of the present invention.

FIG. 11 is an explanatory diagram of a local curvature power change of an aspherical surface in a numerical example 4 of the projection optical system of the present invention.

FIG. 12 is an aberration diagram of Numerical example 4 of the projection optical system of the present invention.

FIG. 13 is a lens sectional view of Numerical Example 5 of the projection optical system of the present invention.

FIG. 14 is an explanatory diagram of a local curvature power change of an aspherical surface in a numerical example 5 of the projection optical system of the present invention.

FIG. 15 is an aberration diagram of Numerical example 5 of the projection optical system of the present invention.

FIG. 16 is a lens cross-sectional view of Numerical Example 6 of the projection optical system of the present invention.

FIG. 17 is an explanatory diagram of a local curvature power change of an aspherical surface in Numerical Example 6 of the projection optical system of the present invention.

FIG. 18 is an aberration diagram of Numerical example 6 of the projection optical system of the present invention.

FIG. 19 is a lens cross-sectional view of Numerical Example 7 of the projection optical system of the present invention.

FIG. 20 is an explanatory diagram of a local curvature power change of an aspherical surface in Numerical Example 7 of the projection optical system of the present invention.

FIG. 21 is an aberration diagram of Numerical example 7 of the projection optical system of the present invention.

FIG. 22 is an explanatory diagram of the paraxial refractive power arrangement of the projection optical system of the present invention.

FIG. 23 is an explanatory diagram of aspherical surface processing according to the present invention.

FIG. 24 is a block diagram of essential parts of a semiconductor device manufacturing system according to the present invention.

FIG. 25 is a flowchart of a semiconductor device manufacturing method of the present invention.

FIG. 26 is a flowchart of a semiconductor device manufacturing method of the present invention.

[Explanation of symbols]

Li group i IP image plane M meridional image plane S sagittal image plane Y image height 1 excimer laser 2 Illumination optical system 3 Reticle (object) 7 wafers 909 Projection optical system 900 alignment optical system 911 Wafer stage 918 controller 914 Storage device 913 Inspection device

Continuation of the front page (56) Reference JP 10-325922 (JP, A) JP 10-197791 (JP, A) JP 11-97347 (JP, A) JP 11-95095 (JP , A) JP 10-333030 (JP, A) JP 8-179204 (JP, A) JP 10-154657 (JP, A) JP 10-339842 (JP, A) JP 6-51198 (JP, A) JP-A-6-186476 (JP, A) JP-A-2000-231058 (JP, A) JP-A-2000-235146 (JP, A) JP-A-2000-249917 (JP, A) Open 2000-121934 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 13/24 G02B 13/18 G02B 9/00

Claims (11)

(57) [Claims] 1. A projection optical system for projecting an image of an object on an image plane, the projection optical system comprising, in order from the object side, a first lens unit L1 having a positive refractive power and a first lens group L1 having a negative refractive power. The second lens unit L2 and the third lens unit L having a positive refractive power
3, a fourth lens group L4 having a negative refractive power, a fifth lens group L5 having a positive refractive power, a sixth lens group L6 having a negative refractive power, and a lens group having a positive refractive power L7
Where L is the conjugate length of the projection optical system and φo is the total power of the negative lens groups, 70> | L × φo |> 17 (φo = Σφoi; φoi is the i-th negative group) a power), the height of the axial marginal ray h, when the hb height of the most off-axis principal ray, 15> | hb / h | > 0.35 at least two surfaces of satisfactory surface of the an aspherical surface, the aspherical surface of the second surface the at least, when set to the non-spherical surface of the aspherical amount △ ASPH, 0.02> | △ ASPH / L |> 1.0 satisfy × ^{10 -6,} The at least two aspherical surfaces have two aspherical surfaces each having a region whose local curvature power changes have opposite signs from the center of the surface to the peripheral portion , and the two aspherical surfaces are
The first lens group has two surfaces, or the first lens group and
One surface for each of the second lens groups, or the second lens group
A projection optical system characterized in that it is arranged in . 2. The projection optical system according to claim 1, wherein the at least two aspherical surfaces are located between the first lens surface on the object side and the stop position. 3. A projection optical system for projecting an image of an object on an image plane, the projection optical system comprising, in order from the object side, a first lens unit L1 having a positive refractive power and a first lens group L1 having a negative refractive power. The second lens unit L2 and the third lens unit L having a positive refractive power
3, a fourth lens group L4 having a negative refractive power, a fifth lens group L5 having a positive refractive power, a sixth lens group L6 having a negative refractive power, and a lens group having a positive refractive power L7
Where L is the conjugate length of the projection optical system and φo is the total power of the negative lens groups, 70> | L × φo |> 17 (φo = Σφoi; φoi is the i-th negative group) Power), where h is the height of the axial marginal ray and hb is the height of the most off-axis chief ray, in the second lens group, 15> | hb / h |> 0.35 When a plurality of aspherical surfaces satisfying the above are satisfied and the aspherical surface amount of the plurality of aspherical surfaces is ΔASPH, 0.02> | ΔASPH / L |> 1.0 × 10 ⁻⁶ is satisfied, and At least one aspherical surface of the plurality of aspherical surfaces has a region where the local curvature power gradually increases in the negative direction or gradually decreases in the positive direction from the center of the surface to the peripheral portion. Optical system. 4. The plurality of aspherical surfaces are first on the object side.
The projection optical system according to claim 3, wherein the projection optical system is located between the lens surface and the stop position. 5. The aspherical lens used in the projection optical system, wherein at least one of the aspherical lenses has an aspherical surface on the back surface of an aspherical surface. The projection optical system according to claim 1. 6. The aspherical lens used in the projection optical system is such that the back surface of the aspherical surface of the aspherical lens is aspherical. The projection optical system according to the item. 7. The aspherical lens used in the projection optical system, wherein at least one of the aspherical lenses has a back surface of an aspherical processed surface which is a flat surface. The projection optical system according to claim 1. 8. The aspherical lens used in the projection optical system is such that the back surface of the aspherical surface of the aspherical lens is a flat surface. The projection optical system described. 9. A pattern on a first object illuminated by light from a laser light source using the projection optical system according to claim 1 to project onto a second object for exposure. And a projection exposure apparatus. 10. A pattern on a first object illuminated by light from a laser light source using the projection optical system according to claim 1, and a pattern on the second object A projection exposure apparatus, which scans, projects, and exposes both of the second objects in a direction perpendicular to the optical axis of the projection optical system at a speed ratio corresponding to the projection magnification. 11. A device is manufactured by projecting and exposing a pattern on a reticle onto a wafer surface by using the projection optical system according to claim 1, and then subjecting the wafer to a developing process. And a method for manufacturing a device.